Upstream (software development)

This article appears to be a dictionary definition. Please rewrite it to present the subject from an encyclopedic point of view. (May 2023)

In software development, when software has been forked or uses a chain of libraries/dependencies, upstream refers to an issue that occurs in software related to the chain. It is the direction that is toward the original authors or maintainers of software. It is usually used in the context of a version, a bug, or a patch.

Upstream development allows other distributions to benefit from it when they pick up the future release or merge recent (or all) upstream patches.^[1] Likewise, the original authors (maintaining upstream) can benefit from contributions that originate from custom distributions, if their users send patches upstream.

The term also pertains to bugs; responsibility for a bug is said to lie upstream when it is not caused through the distribution's porting, non-upstream modification or integration efforts.